your problem may be you have the wrong region wad files installed. go back into wad manager and uninstall them (DO NOT DELETE IN SYSTEM SETTINGS!!!)
and download wads of your region ONLY or you might brick your wii.

or use FREETHEWADS before you try install the wad download FREETHEWADS its a .EXE program file all you need to do is drag and drop your wad that you want to use onto the FREETHEWADS.exe file a dos window will pop up for a split second and that will make it region free

you should now be able to load the wad the previously did not work

some however may need additional patching to get them to work ... namely some Japanese Wiiware like Pokemon Scramble!